“Promoting the national water conservation action” and “encouraging the reutilization of reclaimed water” is officially described in “The 14th Five-Year Plan for National Economic and Social Development of China (2021——2025)” and “the Long-Range Objectives Through the Year 2035”. The reuse of reclaimed water in the water-deficient areas is important for the sustainable development of water resources. Reclaimed water-irrigated agriculture can achieve comprehensive economic, ecology and society benefits, and conforms to the national policy requirements of Carbon Peak and Neutrality (namely “Double Carbon”). The fundamental investigation on reclaimed water-irrigated agriculture is generally beginning, and the related achievements can seldom be found. Two kinds of reclaimed water samples from wastewater treatment plants in Xi’an City, the capital of Shaanxi Province in northwestern China and Shenyang City, the capital of Liaoning Province in northeastern China, were recorded as “water sample A” and “water sample B”, respectively, were used in the research, and methods of ultraviolet-visible spectroscopy (UV-Vis), elemental analysis, three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEMs) and Fourier transform infrared spectroscopy (FTIR) was applied to analyze DOM in water samples. The characteristic constants were further discussed to study the detailed information of DOM. The results show taht the absorption regions of 250~270 nm appear in UV-Vis spectra, indicating double-bond structure and aromatic components, and the absorption peaks at 210~250 nm are caused by unsaturated double-bond conjugate structure in DOM. DOM in “water sample A” shows a higher humification degree and a greater relative molecular mass, while it suggests a low polymerization degree of C-skeleton in the benzene ring and a more obvious endogenous feature in DOM from “water sample B”. The nature of DOM can be significantly affected by micro-organisms activities. The DOM fluorescence peaks appear at three locations, which are Ex/Em=280/310 nm (Tyrosine-like components), Ex/Em=230/320 nm (Tryptophan-like components) and Ex/Em=250/460 nm (Humus-like components), respectively. DOM in two water samples are autochthonous and of low-aromaticity, and DOM in “water sample B” is relative fresh and new generated. The FTIR spectra of the two DOM samples are similar, and the representative peaks appear at 3 460～3 420 cm-1 (stretching vibration of —OH and —NH2), 2 925 cm-1 (asymmetric stretching vibration of —CH2), 1 639 cm-1(stretching vibration of CO and bending vibration of N—H) and 1 412 cm-1 (shear deformation vibration of —CH2). Functional groups of DOM in two water samples very little, and the main elements are the protein-like components, carbohydrates and aromatic organic compounds. The achievements are significant to pre-evaluate the environmental behavior and ecological effect of DOM in reclaimed water used for agricultural irrigation.